The invention relates to an apparatus for transporting a recording carrier through a printing station and for moving the recording carrier toward or away from an intermediate carrier at such station of a printing or copying apparatus in which toner images, arranged on the intermediate carrier, of the characters to be printed, are transferred to the recording carrier.
It is known that the paper web which is to receive printed material in the printing station of a mechanical highspeed printer, must be precisely transported through the printing location in order to obtain a clear legible print, and to achieve these results, corresponding paper guides for the paper, forming the recording carrier, are provided. A similar problem also arises in the operation of non-mechanical printing devices, as for example those employing electrostatic printing. Such electrostatic high-speed printers may involve, for example, an electrophotographic high-speed printer mechanism in which the printing information is projected in a light-optical fashion on a photoconductive surface, for example, a drum which is electrostatically charged throughout its entire area. The latent charge-image of the desired information to be printed, produced by such an arrangement, is developed in a developer station with colored powder, normally designated by the term "toner". The image so developed with powder is then transferred in a printing station from the electrostatically charged drum to a recording carrier, such as a paper web, by means of an influencing electrostatic field.
To achieve a satisfactory transfer of the powder image from the photoconductive surface of such intermediate carrier to the paper web, hereafter referred to as the "recording carrier", the latter must be brought into suitable predetermined relationship with the intermediate carrier, for example, must be brought into contact with the latter. However, the recording carrier must be capable of being readily removed from engagement with the intermediate carrier, as for example during pauses in the printing operation, or during apparatus malfunctions. Further, it must also be additionally assured that, following start of the transport of the recording carrier, the information on the intermediate carrier is transferred from the surface thereof to the recording carrier at the desired location. Likewise, in connection with the stopping of the recording carrier, it must be assured that the last possible line of the toner image on the intermediate carrier is properly transferred onto the recording carrier. Thus, the achievement of a satisfactory transfer of a toner image on the intermediate carrier requires that a series of conditions must be satisfied.
U.S. Pat. No. 4,131,358 (corresponding to German OS No. 2,636,326) discloses an apparatus for effecting a movement of a recording carrier to and from an intermediate carrier. In this construction, two saddle members are provided for controlling the position of the recording carrier relative to the intermediate carrier. In such construction the saddles are pivotally supported on respective axes, with such saddles being symmetrically arranged, relative to the location of the surface of the intermediate carrier at which the recording carrier is to be disposed, in close relationship to the intermediate carrier. Each saddle has a first recording carrier-engaging zone at one side of its pivotal axis, and a second carrier-engaging zone at the other side of its pivotal axis. These engaging zones are so designed that the recording carrier is engaged and adequately tensioned in each of the respective positions of the saddles.